Along with the continuous development of outlets, plugs and switches with ground fault circuit interrupter function (GFCI), the requirements for function and operational safety of GFCI outlets and plugs are getting higher and higher, especially for American outlets and plugs.
American outlets are usually installed inside the wall, have one pair of power supply input wiring terminals to connect with the live wire and neutral wire in the wall, one pair of power supply output wiring terminals to connect the external power wire to put out the live wire and neutral wire, and several groups of power supply output holes to connect power supply plugs.
American outlets often have an electric leakage detection protective circuit inside, which can automatically cut off the power output of the outlet as protection when there is such fault as electric leakage, short circuit etc. in the power supply circuit. But some outlets have a defect in the design: when the installation personnel mistakenly connects the live wire and neutral wire inside the wall with the power output wiring terminals of the outlet, the electric leakage detection protective circuit inside the outlet cannot detect this fault of wrong wiring.
In case the user uses a mistakenly wired outlet, it may not function as electric leakage detection protection and there may be accidents of burning electric apparatus and electric shocks.
In addition, since an American outlet has one pair of power input wiring terminals, one pair of power output wiring terminals and at least one group of power output holes, there are at least three live wire conductors independent from each other and at least three neutral conductors independent from each other. When a reset button of an outlet is at a trip position, three live wire conductors are independent and disconnected from each other; when the reset button of the outlet is at a reset position, three live wire conductors are connected with each other via the circuit. Similarly, when the reset button of the outlet is at a trip position, three neutral conductors are independent and disconnected from each other; when the reset button of the outlet is at a reset position, three reset conductors are connected with each other via the circuit.
Owing to the compact size of power outlets, in order to realize the synchronous operation of three power conductors, rapid contact and cutout, and elimination of sparks, high requirement for fabrication process and high fabrication cost are required.